1. Field of the Invention
This invention relates to packaging. In particular, the invention relates to stacking integrated circuit (IC) devices.
2. Description of Related Art
Demands for high density boards in microprocessor systems have created many challenges to the board assembly process. Among several methods, stacking multiple integrated circuit (IC) devices saves a significant amount of space on printed circuit board (PCB).
Existing techniques to stack multiple IC devices have a number of drawbacks. One technique solders the pins of the top device onto a flexible interconnecting element which is bent to be soldered to the pins of the bottom device. Another technique bends the pins of the top device and soldering the bent pins to the upper portion of the pins of the bottom device. Yet another technique solders the underneath area between the heel and the toe of the J-lead pins of the top device onto the surface area between the heel and the toe of the J-lead pins of the bottom device. These techniques have several disadvantages. First, the mechanical support is weak leading to easy mechanical failure. Second, the soldering is not solid and usually does not follow common manufacturing standard which may lead to unreliable electrical contacts.
Therefore, there is a need to have an efficient technique to stack multiple IC devices.